Ferroelectric ceramic storage display tube

ABSTRACT

A ferroelectric ceramic is mounted within a CRT in a &#39;&#39;&#39;&#39;strainbiased&#39;&#39;&#39;&#39; state, so that it is birefringent. A reflective layer is mounted adjacent the ceramic, and a photoconductive layer is mounted adjacent the reflective layer. With a potential applied across the ceramic-photoconductive layer combination, an image written upon regions of a phosphor target adjacent the photoconductive layer by an electron beam, results in the flow of local charge through corresponding regions of the ceramic, thereby changing the polarization thereat. The flow of polarization charge acts to modulate the birefringence in the ceramic, in accordance with the pattern of the image. A corresponding pattern of brightness is then projected upon an external screen. A &#39;&#39;&#39;&#39;scattering mode&#39;&#39;&#39;&#39; arrangement is also employed.

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Kazan v 1 r i =11 5 t .o y f 541 FERROELECTRIC CERAMIC sTo'RAoEY g i ogidgag sysr inj y aj DISPLAY TUBE l een. new V v ;;.'1'-'- in..- a. l [75 Inventor: Benjamin Kazam Bedford Hill's, Primary Exammer1:e"e Fears =5 I a Attorney, Agent, or Fzrm- John A. Jordan I i v t v [73] Assignee. International Business Machines l Corporation, Armonk, N.Y. [57] ABSTRACT v V p U g i p A ferroelectric ceramic is mounted within a CRT in a l [22] J 1972 I strain-biased state, so that'it is birefringent;- A -re- [21] .A l, M 267,750 7 flective layer is mounted adjacent the ceramic, and a photoconductive layer is' mounted'adjacent the'r'eflecv H tive layer. With a potential applied across the ceramic- [52], C 340/1731 178/785 178/75 photoconductive layercombination, an image written 340/173 340/173 340/173 CR upon regions of a phosphor'target adjacent the photo- [51] II-lt. Gllc conductive layer y an electron beam, results in the [58] Field of Search 178/75 D; 340/1732, flow of local charge through corresponding regions of it the ceramic, thereby changing the polarization y l thereaLThe flow of polarization charge acts to modu- [561 References and I late the birefringence in the ceramic, in accordance UNITED STATESIPATENTS with the pattern ofthe image. A corresponding pat- 1 3,659,270 4/1972 Maldonado .L....'340 173.2 tern of brightnessis then, projected upo n. external: OTHER PUBLICAUONS scgezrg. A iscattering modei arrangement isalsoem- IBM Tech. Dis. Bul. v01v 5, No.-3, Aug. 1962 pp. p y T 54-56. 7 Claims, 2 Drawing Figures FERROELECTRIC CERAMIC STORAGE DISPLAY TUBE BACKGROUND or 'r iii iisivEiiT IoN i cent photoconductive layer, in accordance with the degree of excitation caused by the beam. The local conductivity, in turn, allows a flow of local polarization ted through the prism, brightness variations are proerased. In additiompresent day storage display tubes suffer from the fact that dynamic or rapidly changing images cannot be displayed without disturbing the stored image. Moreover, present day tubes presently considered most promising for computer terminal applications, suffer from the additional shortcomings of exhibiting low brightness (marginal in many applications), and the inability to store and display half tone information. Typical of such type tubes, is the bistablephosphor cathode ray storage display tube (CRT).

In addition to storage display devices of the tubevariety, other type storage display devices have been developed in which the input information must be in optical form. Typical of such storage display devices, is that described by J. R. Maldonado et al. in the Proceedings of the I.E.E.E., Vol. 59, No. 3, March 197 l pp. 368 etc., in an article entitled Strain-Biased Ferroelectric-Photoconductor Image Storage and Display Devices. To address such a device requires an auxiliary cathode-ray tube or a modulated scanning light beam. This results in complex and bulky equipment which may also be expensive.

SUMMARY OF THE INVENTION In accordance with the principles of the present invention, a ferroelectric ceramic storage display tube is provided, whereby electrical information can be stored and selectively erased, at high speeds. In addition, in accordance with such an arrangement, non-stored images can be superimposed on stored images, and an electrical readout signal may readily be produced.

To achieve this end, the inner surface of the glass faceplate of a CRT is provided with a transparent conductive coating upon which is mounted a ferroelectric ceramic wafer. The surface of the wafer is then coated with a mosaic of reflecting conductive elements, and the mosaic surface of the conductive reflecting elements is, in turn, coated with a photoconductive layer. The photoconductive layer is then coated with a transparent conductive coating, and the latter is, in turn, coated with a thin layer of phosphor; The ceramic wafer is arranged to be strain-biased," so that it is birefringent. A write potential applied across the transparent conductive coatings acts to develop, in the ceramic wafer, a transverse field having an intensity which is modulated by the local resistivity of the photoconductive layer.

Accordingly, when selected areas of the layer of phosphor are bombarded by an electron beam, in accordance with electrical input signals, the phosphor is locally excited, inducing local conductivity in the adjacharge throughcorresponding areas of the ceramic layer, thereby modulating the birefringence in these areas, in accordance with the pattern written by the electron beam. Then external plane-polarized light, reflected back after passing through the ceramic wafer, exhibits a phase delay pattern of the two perpendicular components of the polarized light wherein the components vary from area to area across the ceramic wafer, resulting in a component of polarization perpendicular to the original polarization 7 direction in accordance with the polarization pattern produced therein, during writing. Since only the latter components are transmitduced in the reflected light which is projected upon a viewing screen, and a pattern of varying brightness corresponding to the stored image is produced.

As an alternative to the strain-biased mode of operating the ferroelectric ceramic wafer, the wafer may be operated in a scattering mode. In such an arrangement, patterns written upon the photoconductive layer, by the electron beam, act to cause local polarization changes in the ceramic wafer, whereby external light reflected by the mosaic of reflecting elements is scattered at local regions, in accordance with the written pattern. This process whereby scattering is produced in a ferroelectric ceramic is described in the paper Scattering Mode Ferroelectric Photoconductor Image Storage and Display devices, by W. D. Smith and C. E. Land, Applied Physics Letters, Vol. 20, No. 4, Feb. 15,1972, pp. 169-171.

It is, therefore, an object of the present invention to provide an improved storage display tube.

It is a further object of the present invention to provide an improved storage and display tube, which tube utilizes a ferroelectric ceramic. I

It is yet a further object of the present invention to provide an improved storage and display device, whereby information to be stored and displayed may be written therein at high speeds.

It is yet still a further object of the present invention to provide a storage display tube arrangement whereby electrical information can be stored and selectively erased at high speeds.

It is another object of the present invention to provide a storage display tube whereby non-stored images can be superimposed upon stored images:

It is yet another object of the present invention to provide a storage display tube capable of providing an electrical readout signal indicative of the information stored and displayed therein.

It is still another object of the present invention to provide a storage display arrangement whereby the information stored therein may be readily projected upon a viewing screen. a

It is yet still another object of the present invention to provide a ferroelectric ceramic storage display arrangement wherein the ferroelectric ceramic is operated either in a strain-biased or scattering mode.

It is a further object of the present invention to provide a ferroelectric ceramic storage and display device wherein the image to be stored and projected thereby I i I bi'ite r"diSjfrekittfeaiidliavn tages of the invention will be'apparent from the following more particular description of preferred embodiing drawings BRIEF DESCRIPTION 'OF THE DRAWINGS DESCRIPTION OF THE PREFERRED *-'EMBODIMENTS'- In the embodiment of FIG. 1, a ferroelectric ceramic layer or wafer is arranged to operate within the envelope 1 of a cathode ray type storage'tube in a strainbiased mode. I

i The overall configuration of'th'etube is, in general, analogous to any of the variety of conventional cathode ray type storage and display tube arrangements, heretofore employed in the prior art. Typically, the envelope land faceplate 3 maybe made of glass, with the faceplate obviously being transparent. The electron writing gun, shown generally at 5, comprises a conventional configuration for producing a focused electron beam which can be scanned across the target structure of the tube. v a

In particular, it can be seen, in the arrangements shown, that electron source 7 acts to emit electrons through focusing element 9, and the field created by the vertical deflection plates 11 and 13. As is well known to those skilled in the art, deflection plates 11 and 13 act to control the vertical position of the electron beam. For the sake of simplicity, horizontal deflection plates have not been shown. However, as is understood by those skilled in the art, the omitted pair of horizontal deflection plates act to control the horizontal position of the electron beam. Thus, by appropriate application of signals to both the vertical and horizontal deflection plates, the electron beam can be controlled so that a pattern orimage can be formed upon an appropriate write surface, i.e., target, within the tube, in conventional fashion. In the embodiments shown in both FIGS. 1 and 2, this write surface comprises a layer 27 of phosphor, to be described in more detail, hereinafter. Electron source 7 is connected, as shown, to the negative terminal of an appropriate dc source 15. Typically, source 15 may be 5 kv. As understood by those skilled in the art, the intensity of the electron beam is modulated by the control grid of the electron source, i.e., electron gun, in accordance with an input signal (not shown), thereby creating a luminescent pattern on the phosphor layer in accordance with the time varying magnitude or the like of the signal.

The inner surface of glass faceplate 3, is provided with a transparent conductive coating or layer 17. Typically, such a conductive layer would be deposited upon.the faceplate. Mounted upon transparent conductive layer 17, is a layer or wafer 19 of ferroelectric ceramic. It isclear, that the ceramic layer 19 may be ments of theinvention, as illustrated in the accompanya 4 forr'nd s par'atelyfarid then cemented to the transparent conductive lay er l7. Alternatively, the ceramic aye ma .bqflsp te ,di El y ne n ucti e layer 17 by any'of a y ariety of conventional techniques, such as byvapordeposition or sputtering techniques Typically,'the ceramic lay'e r would be about l'inch in diam eter, and '2 mils thickfl I g Although not shown in FIG. 1, both the faceplate and the ceramic wafer are maintained in a mechanicallystressed condition so that the polarization direction of the ceramic tends tobe in the direction along the surface of the ferroelectric ceramic. Although anyof a variety of materials may be employed for ceramic wafer 19, so long as such materials are capable of producing birefringence, for purposes. of :examplefor the embodiment of FIGJI, the wafer may be taken as fabricated from fine-grained lead zirconate-lead titanate ferroelectric ceramic materials. I '7 As shown in FIG. 1, the surface of ceramic layer 19 is coated with a mosaic 21 of conductive reflecting elements, comprising, for example, evaporated aluminum. The reflecting elements are, in turn, coated with a photoconductive layer 23. The photoco'nductive material 1 may typically comprise CdS, produced, for example, by

evaporation or sputtering.

The outer surface, i.e., the surface of the electron .beam side, of the photoconductive layer 23 is then coated with a transparent conductive layer or coating 25, akin to transparentlayer 17. In this regard transparent conductive layers 17 and 25 may comprise a thin layer of any of a variety of metals or metal oxides, suchas gold or aluminum metal, or metal oxides such as the oxides of tin or indium. Likewise, these materials may be fabricated by any of a variety of conventional fabricating techniques. Finally, after transparent conductive layer 25 is formed, a thin layer 27 of phosphor is formed thereon, as shown. The thin layer of phosphor may comprise, for example, ZnO, or ZnS, either in powder form, or produced as a continuous film by evaporation. i

As hereinabove indicated, ceramic layer 19, in the embodiment of FIG. 1, is operated in the strain-biased mode. Strain-biasing ferroelectric ceramics is well known to those skilled in the art. Typical of the techniques for achieving a strain-biased condition, are

those'described by J. R. Maldonado et al., cited above. Although not shown in detail in FIG. 1, the ferroelectric ceramic layer 19 may typically be strain-biased to produce a uniform strain condition, by bending the faceplate 3. Thus, after the various layers of transparent conductive material and ferroelectric ceramic have been appropriately bonded to one another and to thefac'eplate, in the sandwich form as shown, the faceplate may be flexed either inwardly or outwardly to produce of the optical indicatrix along the strain axes. The magnitude of the resultant birefringence can then be controlled by an electric field applied in the thickness di- -tioned to terminal 33 so that dc potential 35 acts to apply a dc voltage across the photoconductive layer 23 ferroelectric ceramic wafer 19 combination, interposed between transparent conductors 17 and 25. Typically, dc source 35 would be of the order of 200 volts. This voltage, as applied to the pair of transparent conductive layer electrodes in question, acts to develop in .ceramic wafer 19 a transverse field having an intensity which may be modulated by the photoconductive layer 23.

Initially the ceramic is assumed to be uniformly polarized as a result of previous erasure. When no electron beam is present,the tube is in a dark condition and the conductivity of the photoconductor of layer 23 is negligible. Accordingly, no polarization charges flow through the ferroelectric layer interposed between the biased transparent conductive layers 17 and 25. However, when selected regions of the phosphor layer 27 are bombarded by the electron beam from the electron gun, in accordance with the electrical input signals applied to the control grid thereof to create the image to be written, the phosphor is locally excited, causing local conductivity in the adjacent photoconductive layer 23.

This local conductivity in the photoconductive layer results in a flow of local charge through corresponding regions of the ferroelectric wafer, changing its polarization, thereat. The flow of local polarization charge acts to modulate the birefringence in the ceramic wafer, in accordance with the written image. Accordingly, the field applied across the opposite surfaces of the ferroelectricceramic has an intensity which is modulated by the photoconductive layer 23. When the field is removed, for example by moving switch 31 to terminal 37, the image written on phosphor layer 27 remains stored, as a spatial modulation of the birefringence of the ceramic wafer 19.

With switch 31 in the viewing position corresponding to terminal 37, the applied dc voltage is removed and the image stored in ferroelectric ceramic wafer 19 may then be viewed. in accordance with the principles of the present invention, an optical projection system is employed whereby the mosaic of reflecting elements within the tube, interposed between photoconductive layer 23 and ferroelectric ceramic wafer 19, acts to reflect polarized light, in a polarization pattern corresponding to the stored image. An arrangement some-,

what analogous to these projection techniques, is described by G. Marie, in an article entitled Large- Screen Projection of Television Pictures with an Optical-Relay Tube Based on the Pockels Effect, appearing in the Philips Technical Review, Vol. 30, at pp. 292, etc.

To achieve projection, then, light from an external light source 43 is directed through the polarizing prism image,

45. Polarizing prism 45 may comprise any of a variety of conventional polarizing'prism's. Light entering the polarizing prism45 in'this manner is passed through imagin'g lens 47, and enters the ferroelectric ceramic wafer 'l9as acollimated beam "of plane-polarizedlight; This light is then reflected back; after passing through the ferroelectric ceramic wafer, as shown. The phase delay of the two perpendicular components of the polarized light will vary, from area to area, across the ferroelectric ceramic wafer, in accordance with the polarization pattern produced in the ferroelectric wafer during writing. Accordingly, a projected pattern of varying brightness, corresponding to the stored image, will pass through the polarizing prism 45, reaching-projection screen 49. Since viewing does not disturb the polarization' pattern in the ferroelectric ceramic during the viewing process, this process may be continued indefinitely. I Y

in order to erase, switch 31 is positioned at terminal 39, whereby a negative dc voltage is applied across the photoconductive layer-ferroelectrical wafer combination. Typically, dc source 41 is of the order of l00 volts. if it is desired to erase selected areas, the phosphor layer 27 is locally bombarded by the electron beam in the regions to be erased, allowing charge to flow in the opposite direction through corresponding regions the polarization back to the initial of condition within these regions. Accordingly, light within the erased regions is cut off from the corresponding area of the projection screen 49. in order to erase'the entire the complete surface of phosphor layer 27 is flooded, or scanned by the electron beam. This, then, acts to cause the ferroelectric ceramic wafer to regain its initial state of uniform birefringence, over the entire wafer.

It is clear that, in accordance with the principles of the present invention, a relatively high resolution can be obtained from a small tube. For example, a 50p. thick ceramic wafer or layer is capable of a limiting resolution of 50 line pairs/mm. With a ceramic plate or wafer 2 cm X 2 cm in area, a total of 1,000 line pairs/mm is possible in both the X and Y directions.

Of additional importance, is the fact that high writing speeds may readily be achieved with the arrangement, 7

in accordance with the principles of the present invention. For example, with a tube target area of 4 cm the total polarization charge required for writing or erasing the entire area is about lOOuC. With an electron beam of 5 kv accelerating potential, and a phosphor (such as ZnO) with 5 percent efficiency which emits photons of about 2.5 eV energy, each primary electron will produce 100 photons. if these are all absorbed in the photoconductive layer whose quantum gain is, for example, 100, each photon will allow 100 electrons to flow through the photoconductor. In effect, then, each primary beam electron will cause a flow of IO electrons I through the photoconductive layer and ferroelectric ceramic wafer. With a 10p. amp electron beam, this will result in a current of 0.1 A through the ferroelectric ceramic wafer, where the phosphor is bombarded. This current level will produce the required polarization charge of lOOuC in approximately 1 millisecond, al-

lowing the writing or erasing of the entire target area, in this time period. i

It should be recognized that the arrangement of FlG. 1 is readily capable of a further 'bperating mode. in parof the ferroelectric ceramic wafer, thus shifting 7 ticula r', the a'ria ng em 'erit or FIG/1 'niay be operated'so that the generationof nonstored images may be super im es a iff re t PQl J ni. t e-stared ii la' s Thus, where the' external light' 'so'urce 43 pi ot/ides blue light, for example, the stored image will thus appear in'blue, on the projection screen. On the other hand, if the light emission from the phosphor layer 27 is peaked in the green (matched, for example, to the peak of the absorption curve of CbS), this light may also be seen on the projection screen with appropriate 'minor'changes; Specifically, these minor changes involve replacing the mosaic of opaque reflecting elements interposed between the ferroelectric ceramic wafer 19 and photoconductive layer 23, with a slightlyconducting multilayer thin-film dichroic'filter which acts to transmit green light and reflect blue light. Alternatively, this dichroic filter may comprise a mosaic of isolated elements having a relatively high conductivity. In accordance with this latter arrangement, the phosphor may be scanned, as'in a conventional CRT, producing dynamic or moving images on the viewing screen in green light, without disturbing the stored image (viewed in blue light). Under such operatingconditions, switch 31 is maintained in the viewingposition at terminal 37, thus preventing-any changesin polarization in the ferroelectric ceramic wafer.

It should also be recognized that the arrangement shown in FIG. 1 is capable of providing an electrical output signal, corresponding-to the stored image information. To achieve this end, switch 31 is positioned to the erase condition at terminal 39, after an image has been stored in ferroelectric ceramic wafer 19. Phosphor layer 27 is then scanned with the unmodulated electron beam. This causes the flow of charge through successive areas of the ferroelectric ceramic wafer where writing had previously occurred. An electrical output signal may therebybe obtained, by monitoring the current flow through one of the transparent conductive layers, of the photoconductor-ferroelectric ceramic sandwich. V

In summary, thenya storage display tube, about 1 inch in diameter, is capable of extremely high writing and erasing speeds (e.g., l millisecond per frame). Such a tube cannot only be selectively erased, but can also be used to present moving or transient images in one color, superimposed on stored images of another color. In addition, an electrical output signal can be obtained, corresponding to the stored information.

In the embodiment of FIG. 2, the configuration of the storage tube shown therein, is essentially the same as that shown in FIG. 1. The basic difference between the arrangements of FIG. 1 and FIG. 2, resides in the fact that the ferroelectric ceramic wafer in FIG. 2 is operated in the scattering mode.

In this mode, no polarized light is used. However, when the ceramic has zero remanent polarization in the direction normal to its surface, it is in a clear or transparent state. When the ceramic is locally polarized by charge flow through it, it scatters light passing therethrough. In addition to operating the ceramic in the scattering mode, an optical projection system is employed consistent with the manner in which the scatter ing mode provides optical information, indicative of the image stored in the ferroelectric ceramic wafer. In

FIG. 2, like reference characters have been employed to identify elements which are the same as corresponding elements in FIG. 1.

plate sineiimga inf an aegi positionsofas to trainees the ferroelectric ceramic wafer," the' faceplate' is mounted in its'normal s'tate'so that no strainis produced upon the wafer. As can be seen, a potential and switch arrangement is provided, in the same manner as I in FIG. 1. 1

Typical ceramics exhibiting the scattering mode may comprise rhombohedral-phase. lead-lanthanum zirconate-titanate (referred to as PL ZT materials) withthe ratio of La, Zr, Ti, about 7:65:35. For proper operation, the grain size of the material should be about 4-5 microns. V H p g ,In the initial state, it is assumed that ceramic 19 in FIG. 2 is in the state of zero remanent polarization, i.e., the clear state. During writing, switch 31 is maintained in the write position at terminal 33 to create a field across the ferroelectric ceramic wafer 19 photoconductive layer 23 combination. Thus, when phosphor layer 27 is bombarded with an electron beam, in accor dance with the pattern or image to be stored, localregions of conductivity corresponding to said pattern, are created in adjacent photoconductive layer23, as hereinabove described. The pattern of conductivity in photoconductive layer 23 acts to effect a corresponding polarization in the ferroelectric ceramic wafer, to thereby establish local scattering sites, corresponding to said patternl These local'scattering sites acttofdifi fuse or scatter light, passing through the ceramic.

' In order to project the image, as stored in the arrangement of FIG. 2, light from external light source 43 is directed through focusing lens 53 onto a small mirror 55. During reading, switch 31 is maintained at ground read position 37 in order to insure no field is applied across the ferroelectric ceramic. The light reflected from mirror 55 is directed through lens 57, whereby a collimated beam of incident light is directed through faceplate 3, transparent conductive layer 17, ferroelectric ceramic wafer 19 onto the reflective surface of re flective layer 21. The light passing through the polarized regions of the ceramic is then diffused by the local scattering sites formed therein. As shown in FIG. 2, the

diffused reflected light from a given scattering site at 51, for example, is focused by lens 57, positioned in the reflection path, to thereby project a light spot or point on projection screen 49, corresponding to the scattering point.

Thus, those areas of the ceramic which are in the erased condition, i.e., do not cause scattering, allow incident light to return to mirror 55, thus not reaching the screen 49. On the other hand, local regions of the ferroelectric where scattering is produced allow a fraction of this light to pass around mirror 55 and therby reach screen 49, where an image is produced.

Thus, it can be seen that for each point in ferroelect'ric ceramic wafer 19 wherein a scattering site has been induced, a corresponding light point is produced on the screen 49. Accordingly, the image written upon phosphor layer 27 acts to produce a stored pattern of scattering sites in ferroelectric ceramic wafer 19, which sites may be optically transformed into a visual image, on a projection screen. i

In order to erase, switch 31 is set to the erase position at terminal 39 whereby a negative potential is applied across the ferroelectric ceramic photoconductor amount of reverse current flow through the ceramic and leaving it in the state of zero remanent polarization. Alternatively, the full beam current could be used for erasing, with switch 31 acting to be closed for a lim ited time so that the reverse charge flow leaves the ceramic in the zero remanent polarization condition. It is evident that a generator producing a negative pulse of controlled width may be'used for this latter purpose.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the'art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a cathode ray-type storage display tube arrangement, the improvement comprising:

a layer of ferroelectric ceramic means mounted v within said tube adjacent the inner surfaceof the display faceplate thereof ina strainbiased condition so as to be birefringent;

a layer of reflective material means mounted adja cent said layer of ferroelectric ceramic means;

a layer of photoconductive material means mounted adjacent said layer of reflective material means;

means to apply a voltage across the combination of said layer of ferroelectric ceramic means and said layer of photoconductive material means to establish an electric field in the thickness direction of said layer of ferroelectric ceramic means which field may be locally modulated by said layer of photoconductive material means in accordance with an image to be stored therein so as to thereby create local polarization charge flow through said layer of ferroelectric ceramic means to modulate the said birefringence therein in accordance with said image;

a layer of cathodoluminescent phosphor means mounted adjacent said layer of photoconductive material means so that when said phosphor means is locally excited by the electron beam of said tube in accordance with the said image to be stored therein, corresponding regions of local conductivity are created in said layer of photoconductive material means in accordance with said image so as to thereby modulate the said birefringence in said layer of ferroelectric ceramic means to create a stored birefringence pattern therein corresponding to said image; and means to reflect plane-polarized light through the said birefringence pattern of said layer of ferroelectric ceramic means from said layer of reflective material means to thereby obtain a polarization pattern corresponding to the said image'stored in said layer of ferroelectric ceramic means. 2. The display tube arrangement as set forth in claim 1 wherein said means to apply a voltage across the said combination of said layer of ferroelectric ceramic means and said layer of photoconductive material means includes a pair of transparent conductive layers respectivelymounted adjacent thereto oneach side "t f;

i 3. The display tube arrangement as set forth in claim 2 wherein said projectionmeans includesa projection screen rot projecting thereon "the" light "i'eflected through said birefringence pattern. 4. The display tube arrangement as set forth in claim 3 wherein said layer of ferroelectric ceramic means comprises lead zirconate-lcad titanate ferroelectric ceramic material. a

5. Ina cathode ray-type storage display tube arrange ment, the improvement comprising: a layer of rhombohedral-phase lead-lanthanum-zirconate-titinate ferroelectric ceramic material means mounted within said tube adjacent the inner surface of the display faceplate thereof and respon-' sive to have selectively produced therein local scattering sites for selectively diffusing light in accordance with a selected pattern; a layer of reflective material means mounted adjacent said layer of ferroelectric ceramic material means;

a layer of photoconductive material means mounted adjacent said layer of reflective material means;

'means to apply a voltage across the combination of said layer of ferroelectric ceramic material means and said layer of photoconductive material means to establish an electric field in the thickness direction of said layer of ferroelectric ceramic material means which field may be locally modulated by said layer of photoconductive material means in accordance with an image to be stored therein so as to thereby create local polarization in said layer of ferroelectric ceramic material means to form a pattern of said scattering sites corresponding to said image to be stored;

a layer of cathodolum'inescent phosphor means mounted adjacent said layer of photoconductive material means so that when said phosphor means is locally excited by the electron beam of said tube in accordance with the said image to be stored therein, corresponding regions of local conductivity are created in said layer of photoconductive material means in accordance with said image so as to 1 thereby effect local polarization in said layer offerroelectric ceramic material means to create a stored pattern of scattering sites therein corresponding to said image to be stored; and means to reflect collimated light through said layer of ferroelectric ceramic material means so that light reflected through said pattern of scattering sites is diffused to form said image.

6. The display tube arrangement as set forth in claim grain size of approximately 4 to 5 microns. 

1. In a cathode ray-type storage display tube arrangement, the improvement comprising: a layer of ferroelectric ceramic means mounted within said tube adjacent the inner surface of the display faceplate thereof in a strain-biased condition so as to be birefringent; a layer of reflective material means mounted adjacent said layer of ferroelectric ceramic means; a layer of photoconductive material means mounted adjacent said layer of reflective material means; means to apply a voltage across the combination of said layer of ferroelectric ceramic means and said layer of photoconductive material means to establish an electric field in the thickness direction of said layer of ferroelectric ceramic means which field may be locally modulated by said layer of photoconductive material means in accordance with an image to be stored therein so as to thereby create local polarization charge flow through said layer of ferroelectric ceramic means to modulate the said birefringence therein in accordance with said image; a layer of cathodoluminescent phosphor means mounted adjacent said layer of photoconductive material means so that when said phosphor means is locally excited by the electron beam of said tube in accordance with the said image to be stored therein, corresponding regions of local conductivity are created in said layer of photoconductive material means in accordance with said image so as to thereby modulate the said birefringence in said layer of ferroelectric ceramic means to create a stored birefringence pattern therein corresponding to said image; and means to reflect plane-polarized light through the said birefringence pattern of said layer of ferroelectric ceramic means from said layer of reflective material means to thereby obtain a polarization pattern corresponding to the said image stored in said layer of ferroelectric ceramic means.
 2. The display tube arrangement as set forth in claim 1 wherein said means to apply a voltage across the said combination of said layer of ferroelectric ceramic means and said layer of photoconductive material means includes a pair of transparent conductive layers respectively mounted adjacent thereto on each side thereof.
 3. The display tube arrangement as set forth in claim 2 wherein said projection means includes a projection screen for projecting thereon the light reflected through said birefringence pattern.
 4. The display tube arrangement as set forth in claim 3 wherein said layer of ferroelectric ceramic means comprises lead zirconate-lead titanate ferroelectric ceramic material.
 5. In a cathode ray-type storage display tube arrangement, the improvement comprising: a layer of rhombohedral-phase lead-lanthanum-zirconate-titinate ferroelectric ceramic material means mounted within said tube adjacent the inner surface of the display faceplate thereof and responsive to have selectively produced therein local scattering sites for selectively diffusing light in accordance with a selected pattern; a layer of reflective material means mounted adjacent said layer of ferroelectric ceramic material means; a layer of photoconductive material means mounted adjacent said layer of reflective material means; means to apply a voltage across the combination of said layer of ferroelectric ceramic material means and said layer of photoconductive material means to establish an electric field in the thickness direction of said layer of ferroelectric ceramic material means which field may be locally modulated by said layer of photoconductive material means in accordance with an image to be stored therein so as to thereby create local polarization in said layer of ferroelectric ceramic material means to form a pattern of said scattering sites corresponding to said image to be stored; a layer of cathodoluminescent phosphor means mounted adjacent said layer of photoconductive material means so that when said phosphor means is locally excited by the electron beam of said tube in accordance with the said image to be stored therein, corresponding regions of local conductivity are created in said layer of photoconductive material means in accordance with said image so as to thereby effect local polarization in said layer of ferroelectric ceramic material means to create a stored pattern of scattering sites therein corresponding to said image to be stored; and means to reflect collimated light through said layer of ferroelectric ceramic material means so that light reflected through said pattern of scattering sites is diffused to form said image.
 6. The display tube arrangement as set forth in claim 5 wherein said means to apply a voltage across the said combination of said layer of ferroelectric ceramic material means and said layer of photoconductive material means includes a pair of transparent conductive layers respectively mounted adjacent thereto on each side thereof.
 7. The display tube arrangement as set forth in claim 6 wherein said rhombohedral-phase lead-lanthanum-zirconate-titinate ferroelectric ceramic material has a grain size of approximately 4 to 5 microns. 